414 



THE GEOLOGIST. 



ON CERTAIN CRETACEOUS BRACHIOPODA. 



By E. Ray Lankester, Esq. 



In the Plate accompanying this paper are figured three species of 

 Terebratulse, which the writer lately obtained from the Lower Green- 

 sand beds of the Isle of Wight. Two of them are interesting as 

 being entirely new to these strata in Britain, whilst the third is 

 a remarkable deformity of a rare species. In Fig. 1, 2, 4, a shell is 

 drawn which appears to be identical with the Terebratula Moutoniana 

 of D'Orbigny, a species not uncommon in Erance, associated with 

 T. sella in the Upper Neocomian and Aptian beds of that author. 

 It is somewhat oval in shape, depressed and elongated ; surface 

 entirely smooth. The perforate valve is rather more convex than 

 the other, truncated by a foramen of moderate size ; deltidium very 

 short and small. Nine specimens of this species were obtained from 

 the ferruginous Greensand beds, at Dunnose Point, near Shanklin. 

 This shell, on external examination, is easily distinguished from T. 

 sella, which it somewhat resembles, by the absence of any biplica- 

 tion on the frontal margin. Its internal structure proves it to belong 

 to the section Waldheimia of King, which precludes all doubt as to 

 its specific distinctions from T. sella. It is easily distinguished 

 from JFaldheimia Celtica, Morris, by its less elongated and gibbous 

 outline. The specimen drawn in Eig. 5, 6, 7 is the only specimen 

 of the kind which the writer has obtained. The valves are lenticular, 

 beak much produced, foramen very large and circular, deltidium 

 large. Mr. 8. P. Woodward is inclined, with the writer, to regard 

 tiiis shell as Terebratula depressa, Lamarck (T. nerviensis of D'Ar- 

 chiac), a species which has not hitherto been found, excepting in 

 the Upper (?) Greensand beds of Earringdon, and in the Tourtia of 

 Belgium. Since, however, two species, T. tamarindus and T. oblonga, 

 are already known as common to the strata of Shanklin and Earring- 

 don, it is not surprising that T. depressa should have a similar verti- 

 cal range. In Eig. 8, 9, a curious deformity of the Terebratula 

 Celtica of Morris is drawn. This specimen was obtained from the 

 same locality as the two former species. The beak is very much 

 produced and incurved, whilst a deep furrow or groove runs along 

 the median line of the perforate valve, and a corresponding eleva- 

 tion marks the smaller valve. T. tamarindus, " a rare British creta- 

 ceous fossil " (Dav.), was also obtained in considerable quantities, — 

 Eig. 11. 



The rarity of some species and the paucity of any great variety of 

 the forms of Brachiopoda in the Lower Greensand strata of England 

 as compared with the large number of species characterizing the 

 Continental beds usually considered as their " homotaxis," is some- 

 what remarkable. There is no obvious reason why such forms as 

 T. diplujoides, T. hippopus and others associated with a common 

 British species, T. sella, in the Upper Neocomian or Urgonian beds 



